Method for liquid analysis



Aug. 23, 1960 L. c. THAYER ETAL 2,950,176

WTHOD FOR LIQUID ANALYSIS Filed Aug. 15, 1955 M'ETHD FR LIQUID ANALYSISrates Patent O l 2,950,176 Patented Aug. 23, 1960 contains a largenumber of ingredients which may either tend to corrode Various partswith which the water comes in contact, or to form deposits thereontending to change heat conductance coefficients on such parts.

5 As lan example of the materials found within conventional Louis C.Thayer, Duarte, Michael Cznha, Jr., Temple boiler feed-water, referenceis made to the fact that City, and Malborre W. Greene, Pasadena, Calif.,asvarious basic inhibitor materials such as cyclohexylamine,

signers, by rnesne assignments, to Beckman Instrumorpholine, ammonia,and trisodium phosphate are freme, c, Flieloll, Calif-i a 'CGTPOI'HOU 0fC211 quently added to water in order to raise the pH of it forma withinthe range of from about 8 to about 10 in order Filed Aug y 1955, Sen Nm523,280 to reduce the corrosive tendency of the water. Water usuallycontains various cationic impurities such as sodi- 3 Claims- (CL 23-230)um, calcium and magnesium ions, which may be present along with suchanions as the carbonate ion, the silicate h 15 ion, the chloride ion,the sulfate ion, and the phosphate The present mvemon relates to n eWarid improved ion. The anions may, in general, be divided for practicalmgrllods and Lapparatlls for thebanlyss of hqmdi d purposes into twocategories-strongly or weakly acidic.

*e present Invention may e ne y Sum.manze ab The reactions of anionsfalling within either of these being concerned with procedures andequipment for g y two classes are broadly very similar, and, hence, foranalyzing liqulds such as water for various ionlc in- 1 k t u. b .1 f dt ,h gredients carried therein -by rst measuring the conplaqca ,vor mcon m mg 01er ee 'Wa erf amons ductance of the liquid containing suchions; removing Wlt'hm elmer of these groups may be Considered t0` atleast part of such ions and/or converting other of get-her' such ions todifferent species; and then again measuring A ample 0f' bollfl feed-Wam?may be C0I1S1dfed-aS the conductance of said liquid, so that by usingelectrical Comallmg the 10115 llsfed Undef C611 1 0f Table L Whl'chmeans as will be hereinafter described, the diiferential Wlll be Usedfor @XPIEIUHOYY PUUQOSS 111 further descllb' in the conductivitymeasurements obtained may be diing the invention.

rectly interpreted to indicate the initial ionic concentration withinthe liquid. With the invention a series of cells for measuringconductance is normally employed together with means disposed betweeneach of these cells for selectively treating different classes of ionicingredients.

Direct and continuous measurement of the quantity of various classes ofions present in a liquid presents an extremely ditlicult problem.However, it has been found that by (l) selective removal and/ orconversion of the various classes of ions in a predetermined order, and(2) measurement of the conductance of the liquid before and after eachremoval or conversion step, the initial ionic makeup of the liquid maybe determined. The conversion of all anions to strongly acidic anions atpredetermined intervals permits the highest sensitivity in conductancemeasurements and direct correlation of the indicated variable to theconcentration of dissolved ingredients in the liquid. The presentinvention involves a chemical separation of the ions contained in aliquid, based on the ion exchange properties as cations and anions, andon selective exchange of weak and strong ions on diiferent exchangematerials.

A brief summary of the above category does not actually indicate thetrue scope of an invention, and, by necessity in summarizing `aninvention, terms must frequently be used which are apt to mislead thoseunfamiliar with the full scope of the invention as to the preciselimitations of the inventive concept. Perhaps the present invention isbest explained with reference to one of the materials normally analyzedin accordance with the teachings of it. This material is boilerfeedwater.

It is Well known in the art that `boiler feed-water Therein, variousanions and cations are shown together as if these specic ions wereassociated together in chemical compounds. It will be realized by thoseskilled in the art that this representation in the table is forconvenience only inasmuch as a fundamental definition of ions Within aliquid such as water indicates that such ions are not, strictlyspeaking, chemically combined, but are in the nature of separateentities within the disbursing medium. The cyclohexylamine, R-NH3OH, hasbeen added to the Water as a corrosion inhibitor.

In the accompanying drawings, which are set forth in diagrammatic formfor convenience of explanation:

Fig. l shows the ow system employed with the invention in the treatmentand measurement of liquids in accordance with this disclosure; and

Fig. 2 shows an electrical circuit which is preferably employed with theinvention in conjunction with the various measuring cells indicated inFig. 1.

In carrying out the invention in the analysis of boiler feed-Water, suchwater is passed through a iirst conductance cell labeled Cell l, in Fig.l, where the conductance of this water is measured. The water is thenpassed through a rst ion exchange column labeled column 1 in Fig. l,This initial column is used in order to neutralize or remove organicamines from the water, and to replace cations of dissolved salts withhydrogen ions. The result of this initial treatment of boiler feed-waterfrom a chemical standpoint is indicated under Cell 2 of Table i. Theremoval of organic amines and metal cations is substantially complete soas to etlectually constitute a complete stoichiometric conversion of allcompounds present to either water or inorganic acids, the eiiiuent fromcolumn 1 being a mixture of strong and weak acids and water. The weakacids, such as carbonio and silicio, are indicated :sideration in-orderto perform accurate analyses.` Aconversion occurring in column lgreatlyaffects the conas column 2 in Fig. l.

f Y Y s -Y s as un-ionized under Cells 2 and 3 of Table I. However, asmall portion of these weak acids are ionized and the presence of theseweakly acidic anions must be given con- The Vductivity of thefeed-water, increasing this conductivity by "approximately 360% in manyinstances.

The desired conversion in column 3l may be obtained by Vusing therein astrongly acidic ion exchange material such asV sulfonated polystyreneresin on the hydrogen cycle.

. Some particularly suitable resins of this type are those currentlyknown by the trade-names Amberlite 120,

DowexV 50 and ermutit Q.- y'

After the feed-water has been passed through column 1,

Yit is passed through a second conductivity cell, Cell 2, in 7 Vrelatedto the concentration of weak acid anions only.

Following the process of the invention, the water is next Ypassedthrough a second ion exchange column indicated Therein strongly acidicanions, Y Y such as the sulfate ion, the chloride ion and the phosphateion, are removed, leaving the weak acids remaining in the efuent fromthe iirst ion exchange column l unaltered chemically. The chemicalchange produced as a result of Ythe second ion exchange column treatmentis indicated under Cell 3 ofV Table I.

^ The conversion of the strongly acidic anions to hydroxyl anions, whichin turn combine with the hydrogen cations present to form water, may beobtained by using a weakly basic ion exchange material, such'as apolyamine phenol-formaldehyde resin, on the hydroxyl cycle. Somesuitable resins of this category are those currently -knownby thetrade-names Amberlite lR-4B, Dowex 3 and Permutit W.

Following this step, the conductivity of the water leaving column 2 ismeasured, using measuring Cell 3 indicated in Fig. 1. The measurementobtained with this step may be used in conjunction with the measurementsobtained in Cells l and 2 so as to derive a further indication asvto'thecomposition of the initial boiler feed-water, as will be more fullyindicated subsequently. Since the YWeak acids contained in the eiuentfrom column 2 are only slightly ionized, it is ditiicult to obtainaccurate conductance measurements thereon. To surmount this problem, inaccordance with the process of the invention, the Aweakly acidic anionsare converted to strongly acidic anions which will be present in ahighly ionized state. As the weakly acidic anions are converted, more ofthe weak Vacids become ionized, the conversion continuing until all ofthe weak acids are converted to strongly acidic ions.

The boiler feed-water is next passed through a third ion exchangecolumn, column 3 of Fig. l, where the Vvery weakly acidic ions arereplaced by a stronger acidic ion, such as a nitrite ion, and hence theconductivity of the solution is increased. This treatment in the'thirdion exchange column has the chemical effect indicated under Cells 3 and4 of Table I above. The change in conductivity is suicient so that itmay be easily and conveniently measured using conventional conductivitycells with a minimum of difficulty, obtaining significant conductivityreadings.

The desired conversion in column 3 may be obtained by using therein astrongly basic ion exchange material, such as a quaternary aminepolystyrene resin operating on a strongly acidic anion cycle, such as anitrite cycle. Some particularly suitable resins for use with this stepof V1aasonvfs 4 the invention are those currently known by thetradenames Amberlite IRA-400,*Dowex 1 and Permutit S.

The water passing from column 3 is preferably passsed through anotherconductivity CellV 4, indicated in the drawings. The value of theconductivity obtained in Cell 4 may be further usedfiu determining thecontent of the initial feed-water, as will be subsequently indicated.

Water from the conductivity Cell 4 is next passed through anotherexchange column, identified as column 4 in the drawings. Here theYstrongly acidic anion placed into the Water as a result of thetreatment in column 3 is removed, resulting in the complete deionizationof water passed through the complete apparatus of the instant in- Yvention. The reaction taking place in the ion exchange column 4 isindicated under Cells'4 and 5 of Table I.

The desired conversion in column 4 may be obtained by using therein astrongly basic anion exchange material, such as the quaternary aminepolystyrene resin, indicated in the preceding in conjunction with column3, but operating on the Vhydroxyl cycle. The material indicated assuitable for use in column 3 is also suitable for use in column 4.

ductivity Cell 5, las indicated in Fig. l.

-should be zero.

The eliiuent from column 4 is passed through con- Theoretically, theconductivityk of the water passing through this cell Unfortunately, theion exchange operationsV carried out in accordance with this inventionare not always effective to the maximum possible extent, and, as aresult, some ions such as sodium may still be present within the waterpassing through Cell 5, causing this water to have some small amount ofconductivity. It is necessary with the invention to take this unwantedconductivity into consideration if exceedingly accurate results are tobe obtained using the procedure herein described.

It is indicated inthe preceding discussion that, from the ve differentconductivity measurements described, the proportion of various classesof ionic ingredients in the liquid may be calculated. It is consideredunnecessary within the scope of this specification to set forth theprecise derivation of the calculations made inasmuch as such -aderivation is within the skill of the average analytical chemist.However, the various values desired may be obtained utilizing thefollowing formulas given in Table II, where the conductivities measuredby the various cells are designated by the letter g followed by thenumber of the measuring cell, the results being given in parts permillion:

Table Il Concentration:

Strong acid salt 0.29 (g2-gs) Weak acid salt 0.57(g3-g5) Very weak acidsalt". 0.l2(g4-2.2g3) Total dissolved solids 0.29 (g2-g3) +0.57 (go-g5)-l- 0.l2(g4-2.2g3) Inhibitor (g1-g5) [Total dissolved solids] The termtotal dissolved solids given in Table II is to be considered assynonymous with the total quantity of ions present within the waterbeing treated in accordance with the invention.

The numericalY value of the factors by which the measured conductancesare multiplied is based upon a prior chemical analysis of the liquidbeing analysed.V The continuous analysis produced by the practice of theinvention will give an accurate analysis of the Vfluid for Yvariationsfrom the prior chemical analysis as great as i20%. However if a newsource for the boiler feed water'of the example were selected it wouldbe necessary to make an analysis of this new water and adjust themultiplying factors accordingly. v

Since the conductivities obtained in accordance with this invention areadditive, the results indicated in Table II can be obtained electricallyby means which give a direct indication-of 4each, of .the abovequantities on a continuous basis, and, further, various conventionalrecording equipments may be employed so as to keep an accurate log ofthe variation in boiler feed-water.

The present invention is not to be considered as being limited to theprecise operational steps or sequence of operations indicated in thepreceding discussion. As an example of this, it is possible to use themeasurements carried out in Cells l and 2, indicated in the accompanyingdrawings, without conducting the remainder of the operations describedin the foregoing in obtaining an indication as to certain ingredientswithin boiler feed-water or other liquids. It is, therefore, to beconsidered as an object of this invention to provide a method for theanalysis of `a liquid which consists of the steps of measuring theconductivity of such liquids before and after a treatment operationdesigned to convert a certain class of ionic compounds in such liquid toa different class. The breadth of this object is not to be minimized, asthe single conversion step specified in it may be a conversion stepusing a strongly acidic ion exchange material, or other classes ofrelated materials. Further, the conversion step may, under somecircumstances, be replaced by other treatments, suci; as, for example,treatments with ya buffering material which is designed to lower orincrease the conductivity of a iiquid. it should be clear that whereeference is made to the removal of ions from a liquid that a replacementis inferred, the reaction taking place with an ion exchange materialbeing the mutual transfer of ions between the liquid and the exchangematerial, resulting in a substitution or conversion in the ion content othe liquid.

The invention may be utilized in the analysis of iiuids for constituentswhich are essentially non-ionic in nature. Such a compound would be veryslightly dissolved producing a few ions. These ions would be removedfrom solution and ions of a different species substituted therefor oncontact with a suitable ion exchange material. As these ions are removedadditional small amounts of the compound go into solution in order toreplace the removed ions, this process continuing until the non-ionicconstituent is totally dissolved.

The various ionic ingredients removed by the ion exchange materialsindicated accumulate within the exchange coi until such time as it isnecessary to regenerate these materials by various means well known tothe art, such as, for example, treatment with acids or bases. s suchregeneration, the various ionic ingredients rn ce collected, separatedand separately analyzed, us g conventional means, so as to determine therecise chemical composition of the ingredients within the liquid. it isan object of this disclosure to provide a process of the class describedin which various ionic ingredients within a liquid are collected so thatthey may he removed from the analysis system after an extended period,and separately analyzed.

An ion exchange column may be removed from the apparatus during theregeneration process or the method indicated g. l may he utilized.Therein each of the columns has a valve J at each end thereof. Duringthe liquid analysis period, each of the valves is set to provide acontinuous now of liquid from cell to cell. 1n the regeneration process,the valve at each end of the column is turned to hlocaV the abovementioned flow and a suitable regeneration iiquid is passed through thecolumn from an external source not shown.

While boiler feed-water has been indicated in the preceding discussion,it is to he understood that the present invention is not limited inscope to the analysis of this specific liquid. Thus, it can be employedwith other fluids, such as, for example, in `a determination of theproportions of sodium and potassium salts present in a liquid by theexchange of the sodium ions for potassium ions followed by an exchangeof the potassium ions for other species. y

An electrical circuit for continuously performing the '5 computationsindicated in Table 1I is shown in Fig. 2 wherein the conductivity cells1 through 5 of Fig. l are designated by numerals 11 through 15,respectively. A load is connected in series with each of theconductivity cells and the series combination of cell and load isconnected to an alternating current power source 16. Identical loadcircuits are connected with each cell and the circuitry associated withcell 11 will be described as typical. A transformer 17 has a primarywinding 18 connected in series with the cell 11 across the power source16. A secondary winding 19 of the transformer 17 is connected to a fullwave rectifier 21 and the rectified output of the rectier 21 isconnected across a variable resistor 22 and a potentiometer 23. Thevariable resistor 22 and the corresponding resistor associated with theother cells are adjusted to produce equal voltages across each of thepotentiometers when identical liquids are in each of the cells, therebycompensating for variations in cells and circuit components.

If the conductance coupled in series with the cell 11 by the primarywinding 1S is very large in comparison to the conductance of the celland liquid contained therein, the voltage developed across the primarywinding will be very nearly directly proportional to the conductance ofthe cell. 'Therefore, the diiference between the voltages developedacross two of the loads will be substantially directly proportional tothe difference between the conductances measured by the associated cellsand hence directly proportional to the change in ionic content producedby the intervening ion exchange column or columns.

The load circuitry of cells 12 and 14 are each provided with a singlepotentiometer 24, 25, respectively, the load circuitry of cell 13 isprovided with four potentiometers 26, 27, 28, 29 and the load circuit ofcell 15 is provided with three potentiometers 32, 33, 34. The parallelconnected potentiometers are used with cells 13 and 15 because theoutputs of the respective cells are present in more than onecomputation; however, the same result could be obtained utilizing asingle resistor with each cell, the resistor having a plurality of tapsthereon. It is to be noted that a resistor could lbe substituted for theprimary winding 18 and that the rectifier 21 could be omitted withoutaffecting the method of computation. The circuit illustrated ispreferable in that the transformer coupling permits the loadpotentiometers to be electrically isolated from the cells therebyfacilitating switching and interconnection of the various potentiometersand the use of direct current voltages eliminates diiculties due tophasing differences.

The various computations which are performed by the circuit of Fig. 2 togive the analysis of the boiler feedwater are set out in Table III andcorrespond to the formulas given in Table II:

Table III Meter Switch Position a Totsiinhibnorg1 5.2992 0.02m

0.1294 @aan 02992-02993 Ooms-0.5795

The computations are performed by adding and/or subtracting theindicated portions of the outputs of the various conductivity cells. Forexample, the quantity of strong acid anions in the water is determinedby subtracting 9.29 of the output of cell 13 from `0.29 of the output ofcell 12, the diierence voltage being determined by a meter 41. The metermay be provided with a suitable scale so that it can be read directly inparts per million. The other quantities of Table III are determined bymeasuring the voltages appearing at meters 42,743,744, 45 andv45. S-l,S-Z and S3 indicate the three elements Yof a three-position triple poleswitch. The switch is thrown to position 1, position 2 or position 3 asindicated in Table III for the desired computation. The meters 41through Yi6 yshould be of the potentiomfeter type drawing zero currentwhen balanced and should be provided with normally open switches so thatthey are connected in the circuit only when a reading is Vbeing made.'This is done in order to prevent the meters from adding undesired loadson the computingcircuitry.

Since changes could be made in the above method and apparatus and manyapparently widely dilerent embodiments of this invention could be madewithout departure from the scope thereof, it is intended that all mattercontained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

We claim as our invention:

1. A method of continuously analyzing water Vcontaining amonio andcationic compounds disposed therein =for said ionic compounds, whichcomprises: measuring-the conductance of said water; passing said waterthrough a cation exchange material so as to replace the cations otherthan hydrogen Within said Water with hydrogen ions; measuring theconductance of said liquid after it has been passed through said cationexchange material; comparing the two measured conductances to determinethe dier- 'ence therebetween, the change in conductance being a`function of the quantity of cations replaced by said cation exchangematerial; passing said water through an anion exchange material so as toreplace the anions other than hydroxyl within said water with hydroxylions, causing the formation of water; measuring the conductance of saidwater after Yit has been passed through said anion exchange material,with said water being passed through said exchange materials in acontinuous stream and with Ysaid conductance measurements being made atthe same time; and continuously comparing the three measuredconductances to determine the diierences therebetween, the changes inconductance being functions of the quantity of anions within said Water.

A 2. A method of continuously analyzing Water containing anionic andcationic compounds disposed therein for said ionic compounds, whichcomprises: measuring the conductance of said water; contemporaneouslyproducing a first electrical signal representative of the conductance;passing said water through a iirst ion exchange material so as toreplace the cations other than hydrogen within said water with hydrogenions; measuring the conductance of said water after it has been passedthrough said first ion exchange material; contemporaneously producing asecond electrical signal representative of the conductance; passing saidwater through a second ion exchange material so as to replace the anionsother than hydroxyl within said water with hydroxyl ions, causing theformation, of Water; measuring the conductance of said Water after ithas been passed through said second ion exchange material, with saidconductance measurements being made at the same time; contemporaneouslyproducing a third electrical signal representative of the conductance;and combining predetermined portions of said electrical signalsproducing rst and secondy resultant signals, said first resultant signalbeing proportional to the quantity of cations other than hydrogen withinsaid water and said 'second resultant signal being proportional to thequantity Vof anions other than hydroxyl within said water.

Y 3. A method of continuously analyzing water for impurities, comprisingthe steps of: measuring the conductance of said water; then passing thewater through at least four ion exchange materials in a continuousstream,

one of said materials being strongly acidic and operating v on ahydrogenL cycle, another of said materials being weaklybasic'andoperating on a hydroxyl cycle, a third of said materials being stronglybasic and operating on a strong acid anion cycle, and a fourth of saidmaterials being strongly basic and operating on a hydroxyl cycle;measuring the conductance of said Water after passing Athrough earch ofsaid ion exchange materials, with said conductance measurements beingmade at the same time; and comparing the measured conductancestoedetermine the difierences therebetween, the changes in conductancebeing functions o the type and quantity of impurities within said water.i

V4 A method of continuously analyzing water for im pn ties, comprisingthe steps of: measuring the conductance of said water; contemporaneouslyproducing a first electrical signal representative Iof the conductance;then passing the waterrthrough at least four ion exchange materials in acontinuous stream, one of said materials being strongly acidic andoperating on a hydrogen cycle, another of said materials being weaklybasic and operating on a hydroxyl cycle, a third of said materials beingstrongly basic and operating on a strongly acidic anion cycle, and afourth of said materials being strongly basic and operating on ahydroxyl cycle; measuring the conductance 'of said water after passingthrough each of said ion exchange materials, with said conductancemeasurements being made at the same time contemporaneously producingadditional electrical signals representative of each of the conductancesmeasured; and adding predetermined portions of said electrical signalsto produce a plurality of resultant signals, each of said resultantsignals being proportional to a particular group of impurities presentthe water.

5. A method for continuously analyzing a liquid to determine theVconcentration of weak and strong acids therein, which comprises:measuring the conductance of the liquid; passing the liquid through aweakly basic ion exchange material in the hydroxyl form so as to convertthe strongly acidic anions in the liquid to hydroxyl ions, causing theformation of water; then measuring the conductance of the liquid; thenpassing the liquid through a strongly basic ion exchange material in astrongly acidic anion form so as to convert the weakly acidic anions inthe liquid to strongly acidic anions; then measuring the conductance ofthe liquid, with said liquid being passed through said exchangematerials in a continuous stream and with said conductance measurementsbeing made at the same time; and continuously comparing the measuredconductances to determine the `differences, therebetween, the changes inconductances being functions of the concentration of weak and strongacids initially within the liquid.

6. A method for continuously analyzing a liquid to determine theconcentration of weak and strong acids therein, which comprises:measuring the conductance of the liquid; passing the liquid through aweakly basic ion exchange material in the hydroxyl form so as to convertthe strongly acidic anions in the liquid to hydroxyl ions, causing theformation of water; then measuring the conductance `of the liquid; Vthenpassing the liquid through a strongly basic ion exchange material in astrongly acidic anion form so as to convert the weakly acidic anions inthe liquid to strongly acidic anions; then measuring the conductance ofthe liquid; then passing the liquid through a strongly basic ionexchange material in the hydroxyl form so as to convert therstronglyacidic anions in the liquid to hydroxyl ions, causing the formation ofwater; then measuring the conductance of the liquid, with said liquidbeing passed through said exchange materials in a continuous stream andwith said conductance measurements being made at the same time; andcomparing the measured conductances to determine the diiferencestherebetween, the changes in conductances lbeing functions of theconcentration of weak and strong acids initially Within the liquid.

7. A method of continuously analyzing Vwater for impurities, comprisingthe steps of: measuring Vthe conductance of said water; then passing thewater successively through four ion exchange materials in a continuousstream, the first of said materials being strongly acidic and operatingon a hydrogen cycle, the second of said materials being weakly basic andoperating on a hydroxyl cycle, the third of said materials beingstrongly basic and operating on a strong acid anion cycle, and thefourth of said materials being strongly basic and operating on ahydroxyl cycle; measuring the conductance or" said water after passingthrough each of said ion exchange materials, with said conductancemeasurements being made at the same time; and comparing the measuredconduetances to determine the differences therebetween, the changes inconductance being functions of the type and quantity of impuritiesWithin said water.

8. A method of continuously analyzing Water containing anionic andcationic compounds disposed therein for said ionic compounds, whichcomprises: measuring the conductance of said Water; passing said Waterthrough a cationic exchange material so as to replace the cations otherthan hydrogen Within said Water with hydrogen ions; passing said Waterthrough an anion exchange material so as to replace the anions otherthan hydroxyl within said Water with hydroxyl ions; measuring theconductance of said Water after it has been passed through said cationexchange material; measuring the conductance of said water after it hasbeen passed through said anion exchange material, with said Water beingpassed through said exchange materials in a continuous stream and withsaid conductance measurements being made at the same time; andcontinuously comparing the three measured conductances to determine thedierences therebetween, the changes in conductances being functions ofthe quantity of anions and cations initially within said water.

5 References Cited in the le of this patent UNITED STATES PATENTS1,065,246 Held lune 17, 1913 1,175,646 lierer Mar. 14, 1916 lo 1,383,613Simsohn Aug. 23, 1921 1,912,188 Gann May 30, 1933 2,224,382 Douty Bec.10, 1940 2,429,943 Prager Oct. 2S, 1947 2,565,501 Ingram Aug. 29, 195115 2,617,766 Emmett et al. Nov. 11, 1952 2,676,923 Young Apr. 27, 19542,711,995 Sard lune 28, 1955 FORETGN PATENTS 20 721,365 Germany lune 5,1942 OTHER REFERENCES Begremont: Water Treatment Handbook, 1954, pp. 37,41, 42. 5 Samuelson: Ion Exchangers in Anal. Chemt, p.

Calise et al.: Industrial and Engineering Chemistry, vol. 4l, No; l1,November 1949, pp. 2554-63.

Osrnun et al: lndustrial and Engineering Chemistry, vol. 43, May 1951,pp. 1076-78.

TJTTTTTD STATES PATENT oTTTeE CERTIFICATE 0F CORECTIOEN Patent No.2,950q 176 August 23 '1960.

Louis C. Thayer et ala.

it ie hereby Certified that errer eppeere in the printed epeeifieetienof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 1v line 59..Y for "the" read ftheir me; Column 2E Table l, firstcolumnY fourth line thereofi for "304m" read S04: me; same Table lifirst column fifth line thereof for i'l\a++I12PO read Na+-PH2PO4T- en;same Table lY second column, line 2 thereof y for "3H++3C1`" read -sSitka-BaC1m Eef-eg same Table l second columng fifth line thereofU for"'H++H2PG4 read H++H2PO4 column 5,I line l517 for "lioluidsH read liquidcolumn 81, line 24, after "time'l insert a semicolon Signed and sealedthis 18th day of April 1961e (SEAL) Attest:

ERNESTNL SWIDER DVD L., LADD lttest'ing Ooer Commissioner of Patents

1. A METHOD OF CONTINUOUSLY ANALYZING WATER CONTAINING ANIONIC ANDCATIONIC COMPOUNDS DISPOSED THEREIN FOR SAID IONIC COMPOUNDS, WHICHCOMPRISES: MEASURING THE CONDUCTANCE OF SAID WATER, PASSING SAID WATERTHROUGH A CATION EXCHANGE MATERIAL SO AS TO REPLACE THE CATIONS OTHERTHAN HYDROGEN WITHIN SAID WATER WITH HYDROGEN IONS, MEASURING THECONDUCTANCE OF SAID LIQUID AFTER IT HAS BEEN PASSED THROUGH SAID CATIONEXCHANGE MATERIAL, COMPARING THE TWO MEASURED CONDUCTANCE TO DETERMINETHE DIFFERENCE THEREBETWEEN, THE CHANGE IN CONDUCTANCE BEING A FUNCTIONOF THE QUANTITY OF CATIONS REPLACED BY SAID CATION EXCHANGE MATERIAL,PASSING SAID WATER THROUGH AN ANION EXCHANGE MATERIAL SO AS TO REPLACETHE ANIONS OTHER THAN HYDROXYL WITHIN SAID WATER WITH HYDROXYL IONS,CAUSING THE FORMATION OF WATER, MEASURING CONDUCTANCE OF SAID WATERAFTER IT HAS BEEN PASSED THROUGH SAID ANION EXCHANGE MATERIAL, WITH SAIDWATER BEING PASSED THROUGH SAID EXCHANGE MATERIALS IN A CONTINUOUSSTREAM AND WITH SAID CONDUCTANCE MEASUREMENTS BEING MADE AT THE SAMETIME, AND CONTINUOUSLY COMPARING THE THREE MEASURED CONDUCTANCE TODETERMINE THE DIFFERENCES THEREBETWEEN, THE CHANGES IN CONDUCTANCE BEINGFUNCTIONS OF THE QUANTITY OF ANIONS WITHIN SAID WATER.